High-frequency discharge-exciting laser devices are employed for increasing the efficiency of laser output. One example of such a high-frequency di-charge-exciting laser's device is illustrated in FIG. 5 of the accompanying drawings.
Designated in FIG. 5 at 1 is a DC power supply including a regulator circuit for rectifying a three-phase AC input into a DC output and keeping the DC voltage at a constant level as required. A high-frequency inverter 2 converts the DC input into a high-frequency AC output having a frequency ranging from 1 to several MHz. A matching circuit 3 of the .pi.-type serves to gain impedance matching between the output of the high-frequency inverter 2 and a coaxial cable (described later). The coaxial cable, denoted at 4, transmits high-frequency electric power from the high-frequency inverter 2. A laser tube 5 has electrodes 6a, 6brespectively at its opposite ends, and a laser medium gas is circulated in the laser tube 5. By applying high-frequency electric power to the electrodes 6a, 6b, an electric discharge is excited to oscillate and amplify a laser beam in the axial direction. The matching circuit 3 and the laser tube 5 are placed at a considerable distance from the high-frequency inverter 2 and the like.
The coaxial cable has an impedance which is normally of 50 .OMEGA.. Therefore, the coaxial cable is poor in its matching capability with the high-frequency inverter and the laser tube, and a matching arrangement such as for automatic tracking is complex and expensive. The coaxial cable causes a large high-frequency loss. Moreover, coaxial cables which can transmit high electric power are limited and expensive. The coaxial cable limits the distance by which a laser head can be spaced from a cabinet that houses the high-frequency inverter. In addition, the coaxial cable has to be shielded at its opposite ends for protection against radio disturbance.